Growth performance and carcass characteristics of growing-finishing pigs fed diets containing peanut hulls, with or without added probiotic
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Physiological changes occur when an animal experiences stress, these changes are reflected in a shift in the microbial ecology of the gastrointestinal tract (GIT), often to the detriment of the host. Since the early 1950's, producers have relied on the prophylactic use of sub-therapeutic levels of feed-additive antibiotics to protect young pigs, especially during the vulnerable post-weaning phase. Bacteria exposed to repeated doses of antibiotics, whether therapeutic or sub-therapeutic, may develop antibiotic resistance, scientists believe this resistance can be transferred to bacteria in or on non-target species, including humans. Antibiotics also kill bacteria that are known to be beneficial to the host. Consumer concerns about antibiotic resistance have prompted the search for viable alternatives. Two feed-additives that have shown some promise as growth promotants are low levels of dietary fiber and probiotics. Like antibiotics, these feed-additives improve growth by shifting GIT microbial populations but without harming beneficial bacteria. This dissertation is the first in-depth study that combines both low levels of a dietary fiber, peanut hulls (PH), with a probiotic (multiple stabilized enzymes or MSE). Pigs were first fed graded levels of PH (0, 5,10, 15, 20, and 25%) to ascertain the most effective levels to be included in a second experiment, which combined PH (5% and 10% for the grower and finishing phases, respectively) with MSE. Average daily gain increased 19% when 5% PH were combined with MSE in the grower phase but the improvement in gain disappeared when the level of PH was raised to 10%. A third experiment compared the growth of growing-finishing pigs fed a corn-soybean meal diet supplemented with either a popular antibiotic (Tylan 40®) or MSE. There was no difference in grower phase or overall growth performance of pigs fed diets containing either additive although pigs fed MSE grew faster and more efficiently than those fed either Tylan® or the control in the late finishing phase. There is a clear indication that probiotics may act additively, if not synergistically, with low levels of fiber and may offer a safe alternative to antibiotics.